Rheumatoid arthritis (RA) is characterized by destruction of joint structures by proteolytic enzymes released by activated synovial cells. Notably, transforming growth factor-beta (TGF-beta) inhibits proteolytic activity in synovial cell cultures and increased levels of TGF-beta are found in RA in fibroblastic zones near the cartilage pannus junction. Prostaglandin E2 (PGE2) is also at high concentrations in rheumatoid joints. In contrast to TGF-beta, PGE2 increases proteolytic activity, suppresses connective tissue formation, and has potent bone resorbing properties. In previous work, we found that PGE2 selectively inhibits TGF-beta rather than insulin-induced collagen and protein formation in human lung fibroblasts. Although we have identified a specific DNA promoter element which mediates TGF-beta-induced activation of collagen gene transcription, we have been unable to identify a specific PGE2 inhibitory element. These results suggested that the effect of PGE2 on TGF-beta signaling is localized proximal to activation of promoter function. We found that PGE2 decreased binding by 50-60% of a saturating concentration of iodinated TGF-beta to both of the TGF-beta signaling receptors (type I and type II) and inhibited in parallel, expression of both receptor genes in lung fibroblasts. The high concentration of PGE2 in rheumatoid joints, as well as the effect of PGE2 on TGF-beta receptor expression, suggests the possibility that the pathogenesis of rheumatoid joint disease, results, in part, from PGE2-induced decreases in genetic expression of type I and type II TGF-beta receptors on the synovial membrane. To further study regulation of the TGF-beta receptor genes, we isolated the human type II receptor gene promoter, sequenced the first approximately 1000 bp of upstream sequence, and have begun to localize elements required for expression and PGE2 mediated inhibition. For this proposal, I am planning a series of experiments to understand the genetic control of the type I and type II receptor genes in synovial fibroblasts. By transfecting constructs containing cloned type I receptor or type II receptor gene promoters linked to reporter genes, I will determine the cis-acting elements required for expression of these genes in synovial fibroblasts. Following this, I will characterize DNA- nuclear protein interactions which regulate TGF-beta receptor gene expression in these cells. I postulate that similar elements control the two TGF-beta receptor genes in human synovial fibroblasts and that promoter activity will be suppressed by PGE2, acting at a specific DNA site.